Morphological Variations in the Scleral Ossicles of 172 Families of Actinopterygian Fishes with Notes on their Phylogenetic Implications

This study reports on (1) variations in the number and position of scleral ossicles in 283 actinopterygian species representing 172 families, (2) the distribution of the morphological variants of these bony elements, (3) the phylogenetic significance of these variations, and (4) a phylogenetic hypothesis relevant to the position of the Callionymoidei, Dactylopteridae, and Syngnathoidei based on these osteological variations. The results suggest that the Callionymoidei (not including the Gobiesocidae), Dactylopteridae, and Syngnathoidei are closely related. This conclusion was based on the apomorphic character state of having only the anterior scleral ossicle. Having only the anterior scleral ossicle should have evolved independently in the Syngnathioidei + Dactylopteridae + Callionymoidei, Gobioidei + Apogonidae, and Pleuronectiformes among the actinopterygians studied in this paper.